Most likely cause is Negative spring is becoming unclipped in the left leg.
Dissasemble the Air Cartridge and crimp the spring onto the retainer.
Check out the maverick troubleshooting and manuals page

In both cases, I asked Ethan at Maverick and he said that was due to loss of pressure in the damper tube. You can quickly fix it by taking the damping side leg out and just checking the pressure in the damper tube (10 mn job - pressurize the damper tube at 60psi as recommended in the DUC32 fork rebuild manual - page 11). If it's low, pump it up, re-assemble and go test ride to see if that fixes the problem.

If it works, my recommendation is to get a rebuild kit from Ethan and rebuild the fork.

The coil negative spring also works as a top out bumper. The stock one has enough stiffness to resist a clunky top out, but I felt it made the fork sag too much. The next step lighter (4n/m) is great as a negative spring but too weak to prevent a harsh top out. I made a 2 stage rubber negative/top out spring that feels very nice.

Rebound damping clicks and oil weight also affect how hard top out is.

Too little air pressure in the damper will allow it to cavitate on rebound, losing damping and topping out harshly. I run 80psi.